Abstract. A noticeable decrease in seismic noise was registered worldwide
during the lockdown measures implemented in 2020 to prevent the spread of
COVID-19. In Central America, strong lockdown measures started during March
of 2020. In this study, we used seismic stations from Costa Rica, Guatemala, El
Salvador, and Nicaragua to study the effects of these measures on seismic
records by characterizing temporal variations in the high-frequency band
(4–14 Hz) via spectral and amplitude analyses. In addition, we studied the
link between the reduction in seismic noise and the number of earthquake
detections and felt reports in Costa Rica and Guatemala. We found that
seismic stations near the capitals of Costa Rica, Guatemala, and El
Salvador presented a decrease in their typical seismic noise levels, from
200 to 140, from 100 to 80, and from 120 to 80 nm, respectively. Our results
showed that the largest reduction of ∼ 50 % in seismic noise
was observed at seismic stations near main airports, busy roads, and densely
populated cities. In Nicaragua, the seismic noise levels remained constant
(∼ 40 nm), as no lockdown measures were applied. We suggest
that the decrease in seismic noise levels may have increased earthquake
detections and the number of felt reports of low-magnitude earthquakes.
However, the variations observed in several seismic parameters before and
after the lockdown are not significant enough to easily link our
observations or separate them from other contributing factors. Our results
imply that the study of seismic noise levels can be useful to verify
compliance with lockdown measures and to explore their effects on earthquake
detection and felt reports.
COVID-19 lockdown effects on the seismic recordings in Central America